The present invention relates to a thread chaser and chip breaker combination in general and to a chip breaker having a profiled abutment edge and angularly disposed coolant grooves therein in particular.
As is well known in the art, the metallic chips removed from the workpiece by high velocity thread cutting chasers or the like of the type shown in Urbanic U.S. Pat. No. 3,629,887 are exceedingly hot and also, unless broken and/or controlled, may cause damage to the cutting tool, to the workpiece or to both. To alleviate this problem, a chip breaker having a tapered abutment surface with a top edge generally paralleling the root line of the chaser teeth was juxtaposed against the leading edge of the chaser to permit the removed chips to engage the abutment surface for abrasion and breakage thereby. The breaking action afforded by the abutment surface was enhanced by positioning the top edge of the abutment surface as close as possible to the root line of the chaser teeth and thus as close as possible to the crest line of the teeth. This positioning permitted an effective breaking action for most of the chips formed at or adjacent the crest line of the teeth. However, by so positioning the chip breaker, the working pressure on the chaser root line was increased thereby detrimentally affecting the life of the relatively costly carbide chaser. Therefore, these mutually inconsistent design parameters had to be interrelated by positioning the chip breaker only as close to the root line of the chaser teeth as possible for acceptable chaser life while sacrificing the effectiveness of the breaking action on the chips formed at or adjacent the crest line.
The above desribed chip breaker has been slightly modified over the years in attempts to improve the chip breaking action and to increase the operational life of the chaser. As shown in Jennings U.S. Pat. No. 3,126,560, a chip breaker was provided with a shoulder at one end of the beveled or tapered abutment surface adjacent the chaser tooth forming the finished cut. Such shoulder acted to direct the chip or stringer formed by the finishing tooth away from the threaded portion of the workpiece and against the beveled abutment surface for degradation thereby.
Subsequently, as shown in Jennings U.S. Pat. No. 3,176,330, a chip breaker having vertically oriented parallel grooves in its trailing surface mating with the lead face of the chaser directed coolant fluid to the cutting area behind the chip or stringer being formed by the chaser teeth during the metal removal operation. Such coolant introduction by the chip breaker grooves reliably directed the coolant to the chaser cutting edge without the inefficient prior art cutting area flooding procedure, while at the same time cooling the entire body of the chaser by passing the coolant in intimate heat exchange relationship therewith.
Even with the above recited improvements, the placement of the beveled abutment surface of the chip breaker was still controlled by the desired operational life for the relatively expensive chaser. Therefore, the efficiency of the chip breaking action afforded had to be sacrificed by moving the abutment surface away from the chaser teeth to afford such desired life even though the unbroken chips potentially resulting therefrom might cause damage to the chaser and/or to the workpiece.
Accordingly, it is a principal object of the present invention to provide a chip breaker that improves the efficiency of the breaking action without detrimentally affecting the life of the thread chaser.
It is another object of the present invention to provide a chip breaker having an abutment surface with a profile generally corresponding to the chaser cutting edge geometry so that the entire cutting edge of each tooth is uniformly spaced from the abutment surface therefor as required by the amount of material being removed by each such tooth.
It is still another object of the present invention to provide angularly oriented coolant grooves in the trailing or mating face of the chip breaker to direct the coolant fluid against the chip breaker and chaser tooth flanks.
Other objects and advantages of the present invention will become apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principle of the invention may be employed.